Total phenolic content of yacon (Smallanthus sonchifolius) rhizomes, leaves, and roots affected by genotype

Abstract

The content of total polyphenols (TP) in rhizomes, leaves, and tuberous roots of five genotypes of yacon (Smallanthus sonchifolius) from New Zealand, Germany, Ecuador, and Bolivia cultivated on trial field plots of the University of Agriculture in Prague‐Suchdol under field conditions from the 2003 harvest was determined spectrophotometrically by Folin‐Ciocalteau phenol reagent. Obtained results were compared by means of dendrograms according to cluster analyses based on TP and morphological traits. In four genotypes the content of inulin and fructose was also determined. From the obtained results, on the basis of similarity of obtained dendrograms, a very close agreement between TP content in rhizomes and leaves and origin and morphological traits of yacon genotypes was found. Five yacon genotypes were classified into three groups. The genotype from New Zealand with white coloured flesh (NZLw) and genotypes from Ecuador (ECU) and Bolivia (BOL) were distinguished with high TP content in purple coloured rhizomes and leaves; whereas the New Zealand genotype with yellow/orange coloured flesh (NZLy) and the genotype from Germany (DEU) with white coloured rhizomes with purple striations showed lower TP content in rhizomes and leaves. Also, inulin content in genotypes from Ecuador (ECU) and Bolivia (BOL) was higher in comparison to the genotypes from Germany (DEU) and New Zealand (NZLy). Thus, we found that TP and inulin content was dependent on botanical origin, morphological traits and polymorphisms of individual genotypes.